Self-adjusting thermally-responsive electric switch



Feb. 27, 1968 F. BENEDIK 3,371,175

SELF'ADJUSTING THERMALLY-RESPONSIVE ELECTRIC SWITCH Original Filed Oct.9. 1961 i F|G.l.

FIG. 6 m i2 90 '6 f I 47 IN VEN TOR.

FEDOR BENEDIK n TTORNE/ United States Patent Ofiice 3,371,175 PatentedFeb. 27, 1968 3,371,175 SELF-ADJUSTING THERMALLY-RESPONSIVE ELECTRICSWITCH Fedor Benedilr, 19 E. 76th St, New York, NY. 10021 Originalapplication Oct. 9, 1961, Ser. No. 143,641, now Patent No. 3,274,441,dated Sept. 20, 1966. Divided and this application Dec. 23, 1965, Ser.No. 516,046

1 Claim. (Cl. 200-139) ABSTRACT OF THE DISCLOSURE An electrical switchin which a stationary contact is mounted on a support and a movablecontact is carried by a bimetallic element also mounted on the supportand associated with a heater element providing successively a heatingperiod in which the bimetallic element flexes to separate the contactsand a cooling period in which the bimetallic element moves the movablecontact into engagement with the fixed contact. One of the contactmounts is a pivotal mount and a stop element is positioned to be engagedby the heat responsive element when the latter is heated, to cause suchadjustment of the pivotal mount as to maintain a preselected constantcooling period for the heat responsive element regardless of the degreeto which it is heated.

This application is a division of application Serial No. 143,641entitled Sequential Electrical Lighting Arrangement, filed Oct. 9, 196 1and issued as United States Patent No. 3,274,441 on Sept. 20, 1966.

In the aforesaid Patent No. 3,274,441 there is shown an electricalcircuit arange'ment for illuminating a series of lamps in a selectedorder and in a progressive and repetitive sequence. This circuitincludes a series of bimetallic switches consisting of a bimetallicelement and a heater element therefor, each switch being so arrangedthat when the heater element is energized, it heats the bimetallicelement, causing the latter to flex in a direction to open the switchcontacts, and when the heater element is deenergized, the bimetallicelement cools and re turns to its unflexed condition to close the switchcontacts. The circuit is additionally arranged so that the heaterelement of each switch is connected across the switch contacts of thepreceding switch in the series in such a manner that when one bimetallicswitch opens, it energizes the heater of the next switch to cause thebimetallic element of said next switch to flex and open the contactsthereof. Thus, the heating period of each switch is determined by thecooling period of the preceding switch.

It will be appreciated that in the previously described arrangementfor'the progressive illumination of a series of lamps, the opening andclosing periods for the individual bimetal switches can become acritical factor. For example, it is practically impossible to obtain twobimetals with their associated heating elements which react in anidentical manner, and if one of the bimetals of the series requires arelatively long cooling period to return to its closed position, thismeans that the next bimetal is being heated a correspondingly longerperiod than it was designed for, causing it to flex excessively and thusmaking the closing time excessive so that the defect is compounded. As aresult, the heating and cooling periods are constantly increased to thepoint where ultimately the heater coils will be burned out, or at leastthe lighting intervals of the lamps will be too long.

The bimetal switches of the present invention are therefore providedwith a novel structure which makes their operation completelycontrollable and eliminates the aforementioned difiiculties. One benefitof this structure is that the larnp-lighting intervals can beselectively made short, so that the lamps can be illuminated in rapidsuccession.

The present invention contemplates the provision of a bimetallic switchhaving a novel structure which makes its operation completelycontrollable and eliminates the aforementioned difficulties. One benefitof the structure is that when the improved switches are employed in thecircuit arrangement of Patent No. 3,274,441, the lamplighting intervalscan be selectively made short, so that the lamps can be illuminated inrapid succession.

An object of the invention is the provision of a bimetallic switch ofthe type in which the bimetallic element is heated to open the switchcontacts, wherein the switch structure is so arranged and constructedthat the cooling period of the switch may be adjusted to a pre-selectedconstant interval regardless of the period during which the bimetallicelement is heated. As a result, even though the bimetallic element maybe heated to a degree far in excess of that required to open the switchcontacts, once the bimetallic element begins to cool, it traverses aconstant pre-selected distance to close the switch contacts.

In accordance with the invention, there is provided bimetallic switch inwhich one of the switch contacts is frictionally mounted for limitedmovement. A stop is provided for limiting the opening movement of thebimetal, and this stop resets the operating position of thefrictionally-mounted contact so that the switch is selfadjusting forconsistent operation under all conditions. When the bimetal of theswitch is heated and the switch contacts are thus separated, the gapbetween the contacts is a pre-set, constant distance regardless of howmuch the bimetal has flexed under varying durations of heat application.This structure also provides means for the selective setting of theoperating time of each switch, so that the arrangement may be adjustedto illuminate the lamps at uniform intervals in rapid succession, or ata selected slower rate, regardless of the wattage of the lamps employed.

Additional objects and advantages of the invention will become apparentduring the course of the following specification when taken inconnection with the accompanying drawings, in which:

FIG. 1 is an enlarged top plan view of a preferred form of a bimetallicswitch made in accordance with the invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a section taken along line 3-3 of FIG. 1;

FIG. 4 is a diagrammatic plan view of the switch shown in FIG. 1,illustrating the switch in open condition;

FIG. 5 is a diagrammatic plan view similar to FIG. 4, but showing theswitch in a reset, closed position after it has cooled from the openposition of FIG. 4;

FIG. 6 is a top plan view of a modified form of switch made inaccordance with the invention, the switch being shown in closedcondition; and

FIG. 7 is a top plan view of the switch shown in FIG. 6, butillustrating the switch in open and reset position.

Referring in detail to the drawings, the switch illustrated in FIGS. 1-5comprises a bimetallic element or strip 47 carrying at one end a contact48 which engages and makes contact with a stationary contact 49. Thebimetallic strip 47 may be of the conventional brass-steel type, and isso arranged that under heat it will bend in a direction to separate thecontacts 48 and 49. The switch formed by the bimetal is thereforenormally closed in the sense that the contact 48 is in engagement withthe fixed contact 49 when the bimetal is cool, and when the bimetal isheated, the contact 48 is moved away from the fixed contact 49 to openthe switch.

The bimetal 47 has a heating element St} in the form of a coil ofresistance wire wrapped around its body and insulated therefrom. One endof the heating coil is connected at 51 to the body of the bimetal 47while the other end is adapted to be connected to an electrical power .3Source i i l, :bf switches of the type shown herein are partlculaflyintended for use in the sequential lighting g ggg zf shown and describedin my U.S. Patent No. Z a wherein the heating coil of each switch is 2 156 to open the switch contacts during the time that preceding switch iscooling and closing. In such a cir- ..'uit, therefore, the free end ofthe heating coil 50, and the body of the bimetal 47 would be connectedacross the contacts of the preceding switch in such a manner the heatercoil 5% is energized when the preceding switch contacts are open.

In FIG. 1, the bimetal strip 47 is shown carrying the contact 48, isshown in its normally closed position, with the movable contact 48 inengagement with the fixed contact 49, as previously explained. Theintermediate portion of bimetal 47 is covered by a layer ofnon-flammable insulation 64, preferably a thin sheet of asbestos, in theusual manner. The heater coil 50 is wound about this layerof asbestos'64. The end of the bimetal 47 is mounted on a support bracket 65, as bya rivet 66, and the support bracket is in turn mounted on an insulatedbase 67 or the like, by rivets 68.

The fixed contact 49, in this instance, is not mounted rigidly on thebase 67, but is rather frictionally mounted thereon for a limited degreeof movement. For this purpose, the fixed contact 49 is secured to andcarried by an upstanding flange '69 of an electrically conductive plate70 as shown in FIGS. 1 and 3. The plate 70, at its other end, is mountedon a screw bolt 71 which is secured in upstanding position to the base67 by a nut 72. The plate 70 has an aperture '75 which receives theshank of bolt 71, and overlies the nut 72, being held on the bolt 71 byan arcuate leaf spring 73 engaged and depresses at its center by a nut74 threaded on bolt 71. The nut 74 holds the leaf spring 73 underselected tension, so that the conductive plate 70 is pivotally mountedon base 67 with a selected amount of friction. Referring to FIG. 1, itmay therefore be seen that the fixed contact may be frictionally movedin an are about the bolt 71. A terminal lug '78 is also connected tobolt 71 for connection of the contact 49 within the circuit.

The conductive plate 70 also carries a cylindrical stop member 76 whichis eccentrically mounted on the plate 70 by an off-set eyelet or rivet77. This stop member '76 is made of electrically insulating material andis located to engage the free end rear face of the bimetal 47 when thelatter flexes under heat. The distance between the stop member 76 andthe bimetal 47 may be adjusted by turning the stop member about itsoff-center mount 77, so that a selected heating interval for the bimetalmay be obtained before it engages the stop 76.

Where a plurality of the previously described switches are used in thesequential lighting arrangement shown in the aforementioned US. PatentNo. 3,274,441 the heat ing and cooling perids of the individual bimetalscan all be made uniform, and in addition can be selectively adjusted asto duration. It will be observed that when the bimetal 47 in FIG. 1 isheated, it will flex upwardly so that its contact 48 separates from thefixed contact 49. AS the heating continues, the bimetal 47 engages thestop 76 and presses the latter upwardly, causing the plate 70 to :turnin a clockwise direction about its pivot 71 against the frictionaltension of spring 73. This is shown in FIG. 4. The plate 70 willcontinue to turn in this manner, carrying with it the fixed contact 49,no matter how long the bimetal 47 is heated and how much it flexes. Whenthe bimetal cools, it will return to pressing engagement with the fixedcontact 49, but the distance it travels during the cooling period isalways constant and therefore the period in which the switch remainsopen is always constant. More specifically, it will be observed that nomatter how long the bimetal has been heated, when it flexes downwardlyin cooling it travels only the pie-selected and constant distancedetermined by the stop 76 and the fixed contact 49. Thus, the operatingtime for the individual switch is always the same despite line voltagefluctuations, changes in ambient temperatures, variations in the wattageof lamps employed, and other variables which would ordinarily influencebimetal operation. In addition, the inherent variations in performancecharacteristics between the various bimetallic units will not influencethe sequential timing uniformity of the assembly. The heating period ismade slightly larger than required for opening the contacts and may varyfrom unit to unit, but the subsequent cooling period is made thecontrolling factorand this latter is uniform.

In adjusting the series of bimetals for uniform operation, a fiat guagemay be placed between the contacts 48 and 49 of each bimetal to spacethe contacts a desired distance. The eccentric stop member 76 is thenturned until it engages the rear face of the bimetal 47. The guage isthen removed and the plate 9% turned until the contact 49 engages thecontact 48. The bimetal 47 is thus adjusted so that its return distanceduring cooling is equal to the thickness of the guage. Where a pluralityof these switches are employed in the aforementioned sequential lightingarrangement, each of the other bimetals can then be similarly adjusted,so that their operations Will be identical. If an extremely thin guageis employed, the return distances of the bimetals will be very small sothat the lamps will be illuminated in rapid succession.

The contacts 48 and 49 in FlG. 1 are pressed together under a certainamount of tension determined by the amount of friction in the pivotalsuspension of arm 70. This tension is adjusted by nut 74 bearing onspring 73 and is made equal in all units. It is advantageous to make itas small as practicable, as will be seen presently.

Starting from position of FIG. 1, the heater 5i) isenergized, causingbimetal 47 to flex upwardly. At first no physical movement takes placeas the pressure existing between the contacts 48 and 49 is reduced tozero. The time required for this is directly proportional to thepressure existing originally, which in turn depends on the amount offriction. This friction has been made small so as to shorten the timeperiod during which the bimetal is motionless while energized.

Once the contact pressure has been overcome, the 'bimetal proceeds totraverse the gap to the stop 76. Although the heater continues toenergize the bimetal, movement of the bimetal stops when it engages thestop -76. The bimetal now builds up energy until its flexing forceequals the friction in the pivotal suspension of arm 70. This time,incidentally, is equal to the time required previously to separate thecontacts 49, 48.

The bimetal continues flexing, and by bearing against stop 76, itcarries arm 70 along in the same direction it is flexing. This continuesuntil the heater is deenergized. FIG. 4 shows the bimetal position atthis instant, in which the bimetal as well as arm 70 are displaced fromtheir original positions of FIG. 1.

Different unit-s may have inherently different heating characteristics,so that if energized for the same time period, the displacement ofbimetal and arm shown in FIG. 4 may vary from unit to unit. All units,however, will have their bimetals 47 pressing against their respectivestops 76 with exactly the same pressure, since the friction pivot ineach unit has been adjusted to provide the same tension. Furthermore,all units have exactly the same size of gap between the respectivecontacts 48, 49.

When the heater coil 50 is deenergized, the bimetal 47 cools and beginsto straighten out. It has been pointed out that the position of FIG. 4for various units may be different; however, the conditions under whichthe different units will operate in closing the contacts under pressure, are the same. The force residing in the bimetal in straighteningout causes the bimetal to retrace its flexing movement in the reversedirection. Initially the pressure against the stop will be reduced tozero, then the gap will be traversed, and then pressure will be built upbe tween the contacts. Depending upon the temperature, ambient orresidual, the unit may come to rest in a reset position such as shown inFIG. 5, which position is slightly difierent from the original positionof FIG. 1. It is important to note that the unit is ready to start onits heating cycle from either position under the same conditions.

FIGS. 6 and 7 illustrate a modified form of bimetal switch constructionwhich will produce the same controlled and uniform bimetal operation,but in which the bimetal is frictionally mounted for a limited degree oflost motion movement, rather than the fixed contact as in the embodimentof FIGS. 1 to 5.

In FIG. 6 it may be seen that the fixed contact 49 is mounted on aconductive bracket 80 which has an elongated slot 81 receiving screws orrivets 82 for adjustable but secure mounting of the bracket 80 on aninsulated base 83. A generally L-sh'aped arm 84 is secured to the base83, as by rivets or eyelets 85. The arm 84 is electrically conductiveand the rivets 85 may therefore serve as terminal soldering posts forthe bimetal. The bimetal 47 is carried by a conductive strip 86, thelatter having a twisted end portion 87 to which the bimetal 47 issecured, as by a rivet 8-8.

The strip 86 is frictionally mounted on the L-shaped arm 84 in a mannersimilar to the mounting of the plate 70 in FIGS. 1 to 5, and previouslydescribed. That is to say, the strip 86 is loosely mounted on anupstanding bolt 89 afiixed to the arm 84, with an arcuate leaf spring 90overlying the strip 86 and being depressed at its center by a nut 91.The bimetal 47 and its contact 48 can therefore be turned about the bolt89, under frictional tension of the spring 90.

The end of the L-shaped arm 84 has a small projection 92 which islocated to contact the rear face of the free end of bimetal 47 and actas a stop therefor. When the bimetal 47 is heated through energizationof its heater element 50, it will engage the stop 47, so that furtherflexing movement of the bimetal Will reposition its mounting. That is tosay, when the bimetal 47, in the closed position of FIG. 6, is heated,it will flex upwardly, the contact 48 moving away from contact 49. Therear face of the bimetal 47 then engages the projection 92 which acts asa fixed stop and prevents the free end of the bimetal 47 from movingfurther away from the fixed contact 49. As the bimetal continues toheat, it flexes at its center, as shown in FIG. 7, causing the mountedend thereof to turn about the bolt 89. The bimetal thus resets itsmounting position, and the spring 90 and nut 91 maintain this resetposition. On cooling, the free end of the bimetal 47, carrying contact48, need only travel the distance between the projection 92 and thefixed contact 49.

The operational timing of the bimetal 47 may be adjusted by looseningthe screws 82 and sliding the bracket 80 to vary the g p b t een t e fied con ac a h projection 92. A gauge may be used for this purpose, aspreviously explained.

While preferred embodiments of the invention have been shown anddescribed herein, it is obvious that numerous additions, changes andomissions may be made in these embodiments without departing from thespirit and scope of the invention.

What I claim is:

1. A self-adjusting switch comprising a pair of contacts, a support, abimetallic element mounted on the support and carrying a first of saidcontacts, an elongated arm element pivotally mounted at one end on thesupport and carrying the second of said contacts at its free endportion, said elements being positioned on said support such that saidcontacts are normally in engagement with each other, heating meansassociated with said bimetallic element and adapted to be alternatelyenergized and deenergized to provide successive operating cycles, eachcycle consisting of a heating period in which said bimetallic elementflexes in a direction to move said first contact away from said secondcontact, and a cooling period in which said bimetallic element moves thefirst contact back into engagement with the second contact, and a stopmember mounted on the free end portion of said arm in alignment withsaid second contact and spaced a fixed distance therefrom, said stopmember being positioned in the path of flexing movement of saidheat-sensitive element during said heating period and halting movementof said first contact away from said second contact when the contactsare spaced apart a pro-selected distance, whereby said bimetallicelement engages said stop member during the heating period and continuedflexing of the bimetallic element against said stop member turns saidarm about said pivotal mount with the contacts maintained spaced apartby said preselected distance, such that at the end of the heating periodof each successful cycle the contacts are spaced apart by saidpreselected distance and the cooling period for each cycle is maintainedconstant regardless of the duration of the heating period.

References Cited UNITED STATES PATENTS 2,979,585 4/1961 Werr 2001382,771,528 11/1956 Moran 200-122 2,905,790 9/1959 Markham 2001223,077,529 2/ 196-3 Schauer 200122 X 3,243,548 3/1966 Kjellman et a1200-133 FOREIGN PATENTS 721,435 1/ 1955 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

H. A, LEW-ITTER, Assistant Examiner,

